title: Pivotal role of mTOR signaling in hepatocellular carcinoma.
abstract: OBJECTIVE
  The advent of targeted therapies in hepatocellular carcinoma (HCC) has underscored the importance of pathway characterization to identify novel molecular targets for treatment. We evaluated mTOR signaling in human HCC, as well as the antitumoral effect of a dual-level blockade of the mTOR pathway.
  
  
  METHODS
  The mTOR pathway was assessed using integrated data from mutation analysis (direct sequencing), DNA copy number changes (SNP-array), messenger RNA levels (quantitative reverse-transcription polymerase chain reaction and gene expression microarray), and protein activation (immunostaining) in 351 human samples [HCC (n = 314) and nontumoral tissue (n = 37)]. Effects of dual blockade of mTOR signaling using a rapamycin analogue (everolimus) and an epidermal/vascular endothelial growth factor receptor inhibitor (AEE788) were evaluated in liver cancer cell lines and in a xenograft model.
  
  
  RESULTS
  Aberrant mTOR signaling (p-RPS6) was present in half of the cases, associated with insulin-like growth factor pathway activation, epidermal growth factor up-regulation, and PTEN dysregulation. PTEN and PI3KCA-B mutations were rare events. Chromosomal gains in RICTOR (25% of patients) and positive p-RPS6 staining correlated with recurrence. RICTOR-specific siRNA down-regulation reduced tumor cell viability in vitro. Blockage of mTOR signaling with everolimus in vitro and in a xenograft model decelerated tumor growth and increased survival. This effect was enhanced in vivo after epidermal growth factor blockade.
  
  
  CONCLUSIONS
  MTOR signaling has a critical role in the pathogenesis of HCC, with evidence for the role of RICTOR in hepato-oncogenesis. MTOR blockade with everolimus is effective in vivo. These findings establish a rationale for targeting the mTOR pathway in clinical trials in HCC.
authors.affiliation: Mount Sinai Liver Cancer Program, Division of Liver Diseases, Department of Medicine, Mount Sinai School of Medicine, New York, New York 10029, USA.
authors.forename: Augusto
authors.initials: A
authors.lastname: Villanueva
authors.forename: Derek Y
authors.initials: DY
authors.lastname: Chiang
authors.forename: Pippa
authors.initials: P
authors.lastname: Newell
authors.forename: Judit
authors.initials: J
authors.lastname: Peix
authors.forename: Swan
authors.initials: S
authors.lastname: Thung
authors.forename: Clara
authors.initials: C
authors.lastname: Alsinet
authors.forename: Victoria
authors.initials: V
authors.lastname: Tovar
authors.forename: Sasan
authors.initials: S
authors.lastname: Roayaie
authors.forename: Beatriz
authors.initials: B
authors.lastname: Minguez
authors.forename: Manel
authors.initials: M
authors.lastname: Sole
authors.forename: Carlo
authors.initials: C
authors.lastname: Battiston
authors.forename: Stijn
authors.initials: S
authors.lastname: Van Laarhoven
authors.forename: Maria I
authors.initials: MI
authors.lastname: Fiel
authors.forename: Analisa
authors.initials: A
authors.lastname: Di Feo
authors.forename: Yujin
authors.initials: Y
authors.lastname: Hoshida
authors.forename: Steven
authors.initials: S
authors.lastname: Yea
authors.forename: Sara
authors.initials: S
authors.lastname: Toffanin
authors.forename: Alex
authors.initials: A
authors.lastname: Ramos
authors.forename: John A
authors.initials: JA
authors.lastname: Martignetti
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Mazzaferro
authors.forename: Jordi
authors.initials: J
authors.lastname: Bruix
authors.forename: Samuel
authors.initials: S
authors.lastname: Waxman
authors.forename: Myron
authors.initials: M
authors.lastname: Schwartz
authors.forename: Matthew
authors.initials: M
authors.lastname: Meyerson
authors.forename: Scott L
authors.initials: SL
authors.lastname: Friedman
authors.forename: Josep M
authors.initials: JM
authors.lastname: Llovet
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008875:Middle Aged; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases / Q000096:biosynthesis / Q000235:genetics*; D012334:RNA, Neoplasm / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D058570:TOR Serine-Threonine Kinases
chemical_list: D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D012334:RNA, Neoplasm; D058570:TOR Serine-Threonine Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse